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  • Per Process Memory Calculation Alogrithm in Linux (say kernel 2.6 and above)

    - by Vaibhav Singh
    How do you calculate the linux process's Acutal Memory Usage and Not Virtual Memory Usage through the information supplied by /proc//smaps or maps or status or stat. To be more precise I need the heap usage only. I need to do this on an PowerPc based embedded system and hence I do not have utilities like exmap, valgrind etc. I understand the concepts of shared/non shared memory. I have read through the other topics given in this forum about the same but they talk more using the tools mentioned. What I need is the native way of calculation done by the same tools so that I may write a shell script for the same.

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  • php most memory efficient way to return files

    - by bumperbox
    so i have a bunch of files, some can be up to 30-40mb and i want to use php to handle security of the files, so i can control who has access to them that means i have a script sort of like this rough example $has_permission = check_database_for_permission($user, filename); if ($has_permission) { header('Content-Type: image/jpeg'); readfile ($filename); exit; } else { // return 401 error } i would hate for every request to load the full file into memory, as it would soon chew up all the memory on my server with a few simultaneous requests so a couple of questions is readfile the most memory efficient way of doing this? is there some better method of achieving the same outcome, that i am overlooking? server: apache/php5 thanks

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  • Force freeing memory in PHP

    - by DBa
    Hi everybody, in a PHP program, I sequentially read a bunch of files (with file_get_contents), gzdecode them, json_decode the result, analyze the contents, throw the most of it away, and store about 1% in an array. Unfortunately, with each iteration (I traverse over an array containing the filenames), there seems to be some memory lost (according to memory_get_peak_usage, about 2-10 MB each time). I have double- and triplechecked my code, I am not storing unneded data in the loop (and the needed data hardly exceeds about 10MB overall), but I am frequently rewriting (actually, strings in an array). Apparently, PHP does not free the memory correctly, thus using more and more RAM until it hits the limit. Is there any way to do a forced garbage collection? Or, at least, to find out where the memory is used? Thanks in advance, Dmitri

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  • Java ME Runnable object takes up memory although not made an instance yet

    - by user1646684
    I am facing a strange problem with memory in Java ME. here is a part of my code: int variable=1; while (true) { if (variable==2) { display = Display.getDisplay(this); MyCanvas mc = new MyCanvas(this); // MyCanvas is a runnable object mcT = new Thread(mc); // new thread for MyCanvas mc.repaint(); display.setCurrent(mc); mcT.start(); // run thread } if (variable==1) { // Do some other stuff } } The problem is that although still the variable is set to 1, so it does not come through the if (variable==2) condition the program consumes 300kB more memory than when I delete the code after condition if (variable==2). As far as I know the code should by executed and the objects shall be created only when I set variable to value 2. But it consumes the memory also when the code after condition "if (variable==2)" is not executed. Why does this happen?

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  • Android png images big in memory

    - by taivo
    i have an application in android that has an imageflipper. Problem is, after about 8 images loaded to memory, i get an out of memory error. Well, i tried to do dynamic image loading, so that if the user flips 2 images, i'll load next 2 to memory and delete 2 first ones. It kind of works, but it ugly and i have trouble when user flips images back(imageflipper.showprevious()), i can't really shift all images and place new images to the beginning. My question is, is there a better way to do this kind of stuff? Resizing images didn't really help.

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  • Automatic Standby Recreation for Data Guard

    - by pablo.boixeda(at)oracle.com
    Hi,Unfortunately sometimes a Standby Instance needs to be recreated. This can happen for many reasons such as lost archive logs, standby data files, failover, among others.This is why we wanted to have one script to recreate standby instances in an easy way.This script recreates the standby considering some prereqs:-Database Version should be at least 11gR1-Dummy instance started on the standby node (Seeking to improve this so it won't be needed)-Broker configuration hasn't been removed-In our case we have two TNSNAMES files, one for the Standby creation (using SID) and the other one for production using service names (including broker service name)-Some environment variables set up by the environment db script (like ORACLE_HOME, PATH...)-The directory tree should not have been modified in the stanby hostWe are currently using it on our 11gR2 Data Guard tests.Any improvements will be welcome! Normal 0 21 false false false ES X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} #!/bin/ksh ###    NOMBRE / VERSION ###       recrea_dg.sh   v.1.00 ### ###    DESCRIPCION ###       reacreacion de la Standby ### ###    DEVUELVE ###       0 Creacion de STANDBY correcta ###       1 Fallo ### ###    NOTAS ###       Este shell script NO DEBE MODIFICARSE. ###       Todas las variables y constantes necesarias se toman del entorno. ### ###    MODIFICADO POR:    FECHA:        COMENTARIOS: ###    ---------------    ----------    ------------------------------------- ###      Oracle           15/02/2011    Creacion. ### ### ### Cargar entorno ### V_ADMIN_DIR=`dirname $0` . ${V_ADMIN_DIR}/entorno_bd.sh 1>>/dev/null if [ $? -ne 0 ] then   echo "Error Loading the environment."   exit 1 fi V_RET=0 V_DATE=`/bin/date` V_DATE_F=`/bin/date +%Y%m%d_%H%M%S` V_LOGFILE=${V_TRAZAS}/recrea_dg_${V_DATE_F}.log exec 4>&1 tee ${V_FICH_LOG} >&4 |& exec 1>&p 2>&1 ### ### Variables para Recrear el Data Guard ### V_DB_BR=`echo ${V_DB_NAME}|tr '[:lower:]' '[:upper:]'` if [ "${ORACLE_SID}" = "${V_DB_NAME}01" ] then         V_LOCAL_BR=${V_DB_BR}'01'         V_REMOTE_BR=${V_DB_BR}'02' else         V_LOCAL_BR=${V_DB_BR}'02'         V_REMOTE_BR=${V_DB_BR}'01' fi echo " Getting local instance ROLE ${ORACLE_SID} ..." sqlplus -s /nolog 1>>/dev/null 2>&1 <<-! whenever sqlerror exit 1 connect / as sysdba variable salida number declare   v_database_role v\$database.database_role%type; begin   select database_role into v_database_role from v\$database;   :salida := case v_database_role        when 'PRIMARY' then 2        when 'PHYSICAL STANDBY' then 3        else 4      end; end; / exit :salida ! case $? in 1) echo " ERROR: Cannot get instance ROLE ." | tee -a ${V_LOGFILE}   2>&1    V_RET=1 ;; 2) echo " Local Instance with PRIMARY role." | tee -a ${V_LOGFILE}   2>&1    V_DB_ROLE_LCL=PRIMARY ;; 3) echo " Local Instance with PHYSICAL STANDBY role." | tee -a ${V_LOGFILE}   2>&1    V_DB_ROLE_LCL=STANDBY ;; *) echo " ERROR: UNKNOWN ROLE." | tee -a ${V_LOGFILE}   2>&1    V_RET=1 ;; esac if [ "${V_DB_ROLE_LCL}" = "PRIMARY" ] then         echo "####################################################################" | tee -a ${V_LOGFILE}   2>&1         echo "${V_DATE} - Reacreating  STANDBY Instance." | tee -a ${V_LOGFILE}   2>&1         echo "" | tee -a ${V_LOGFILE}   2>&1         echo "DATAFILES, CONTROL FILES, REDO LOGS and ARCHIVE LOGS in standby instance ${V_REMOTE_BR} will be removed" | tee -a ${V_LOGFILE}   2>&1         echo "" | tee -a ${V_LOGFILE}   2>&1         V_PRIMARY=${V_LOCAL_BR}         V_STANDBY=${V_REMOTE_BR} fi if [ "${V_DB_ROLE_LCL}" = "STANDBY" ] then         echo "####################################################################" | tee -a ${V_LOGFILE}   2>&1         echo "${V_DATE} - Reacreating  STANDBY Instance." | tee -a ${V_LOGFILE}   2>&1         echo "" | tee -a ${V_LOGFILE}   2>&1         echo "DATAFILES, CONTROL FILES, REDO LOGS and ARCHIVE LOGS in standby instance ${V_LOCAL_BR} will be removed" | tee -a ${V_LOGFILE}   2>&1         echo "" | tee -a ${V_LOGFILE}   2>&1         V_PRIMARY=${V_REMOTE_BR}         V_STANDBY=${V_LOCAL_BR} fi # Cargamos las variables de los hosts # Cargamos las variables de los hosts PRY_HOST=`sqlplus  /nolog << EOF | grep KEEP | sed 's/KEEP//;s/[   ]//g' connect sys/${V_DB_PWD}@${V_PRIMARY} as sysdba select 'KEEP',host_name from v\\$instance; EOF` SBY_HOST=`sqlplus  /nolog << EOF | grep KEEP | sed 's/KEEP//;s/[   ]//g' connect sys/${V_DB_PWD}@${V_STANDBY} as sysdba select 'KEEP',host_name from v\\$instance; EOF` echo "el HOST primary es: ${PRY_HOST}" | tee -a ${V_LOGFILE}   2>&1 echo "el HOST standby es: ${SBY_HOST}" | tee -a ${V_LOGFILE}   2>&1 echo "" | tee -a ${V_LOGFILE}   2>&1 ## ## Paramos la instancia STANDBY ## V_DATE=`/bin/date` echo "${V_DATE} - Shutting down Standby instance" | tee -a ${V_LOGFILE}   2>&1 echo "" | tee -a ${V_LOGFILE}   2>&1 echo "********************************************************************************" | tee -a ${V_LOGFILE}   2>&1 ## ## Paramos la instancia STANDBY ## SBY_STATUS=`sqlplus  /nolog << EOF | grep KEEP | sed 's/KEEP//;s/[   ]//g' connect sys/${V_DB_PWD}@${V_STANDBY} as sysdba select 'KEEP',status from v\\$instance; EOF` if [ ${SBY_STATUS} = 'STARTED' ] || [ ${SBY_STATUS} = 'MOUNTED' ] || [ ${SBY_STATUS} = 'OPEN' ] then         echo "${V_DATE} - Standby instance shutdown in progress..." | tee -a ${V_LOGFILE}   2>&1         echo "" | tee -a ${V_LOGFILE}   2>&1         echo "********************************************************************************" | tee -a ${V_LOGFILE}   2>&1         sqlplus -s /nolog 1>>/dev/null 2>&1 <<-!         whenever sqlerror exit 1         connect sys/${V_DB_PWD}@${V_STANDBY} as sysdba         shutdown abort         ! fi V_DATE=`/bin/date` echo "" echo "${V_DATE} - Standby instance stopped" | tee -a ${V_LOGFILE}   2>&1 echo "" | tee -a ${V_LOGFILE}   2>&1 echo "********************************************************************************" | tee -a ${V_LOGFILE}   2>&1 ## ## Eliminamos los ficheros de la base de datos ## V_SBY_SID=`echo ${V_STANDBY}|tr '[:upper:]' '[:lower:]'` V_PRY_SID=`echo ${V_PRIMARY}|tr '[:upper:]' '[:lower:]'` ssh ${SBY_HOST} rm /opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/data/*.dbf ssh ${SBY_HOST} rm /opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/arch/*.arc ssh ${SBY_HOST} rm /opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/ctl/*.ctl ssh ${SBY_HOST} rm /opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/redo/*.ctl ssh ${SBY_HOST} rm /opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/redo/*.rdo ## ## Startup nomount stby instance ## V_DATE=`/bin/date` echo "" | tee -a ${V_LOGFILE}   2>&1 echo "${V_DATE} - Starting  DUMMY Standby Instance " | tee -a ${V_LOGFILE}   2>&1 echo "" | tee -a ${V_LOGFILE}   2>&1 echo "********************************************************************************" | tee -a ${V_LOGFILE}   2>&1 ssh ${SBY_HOST} touch /home/oracle/init_dg.ora ssh ${SBY_HOST} 'echo "DB_NAME='${V_DB_NAME}'">>/home/oracle/init_dg.ora' ssh ${SBY_HOST} touch /home/oracle/start_dummy.sh ssh ${SBY_HOST} 'echo "ORACLE_HOME=/opt/oracle/db/db'${V_DB_NAME}'/soft/db11.2.0.2 ">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "export ORACLE_HOME">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "PATH=\$ORACLE_HOME/bin:\$PATH">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "export PATH">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "ORACLE_SID='${V_SBY_SID}'">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "export ORACLE_SID">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "sqlplus -s /nolog <<-!" >>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "      whenever sqlerror exit 1 ">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "      connect / as sysdba ">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "      startup nomount pfile='\''/home/oracle/init_dg.ora'\''">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'echo "! ">>/home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'chmod 744 /home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'sh /home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'rm /home/oracle/start_dummy.sh' ssh ${SBY_HOST} 'rm /home/oracle/init_dg.ora' ## ## TNSNAMES change, specific for RMAN duplicate ## V_DATE=`/bin/date` echo "" | tee -a ${V_LOGFILE}   2>&1 echo "${V_DATE} - Setting up TNSNAMES in PRIMARY host " | tee -a ${V_LOGFILE}   2>&1 echo "" | tee -a ${V_LOGFILE}   2>&1 echo "********************************************************************************" | tee -a ${V_LOGFILE}   2>&1 ssh ${PRY_HOST} 'cp /opt/oracle/db/db'${V_DB_NAME}'/soft/db11.2.0.2/network/admin/tnsnames.ora.inst  /opt/oracle/db/db'${V_DB_NAME}'/soft/db11.2.0.2/network/admin/tnsnames.ora' V_DATE=`/bin/date` echo "" | tee -a ${V_LOGFILE}   2>&1 echo "${V_DATE} - Starting STANDBY creation with RMAN.. " | tee -a ${V_LOGFILE}   2>&1 echo "" | tee -a ${V_LOGFILE}   2>&1 echo "********************************************************************************" | tee -a ${V_LOGFILE}   2>&1 rman<<-! >>${V_LOGFILE} connect target sys/${V_DB_PWD}@${V_PRIMARY} connect auxiliary sys/${V_DB_PWD}@${V_STANDBY} run { allocate channel prmy1 type disk; allocate channel prmy2 type disk; allocate channel prmy3 type disk; allocate channel prmy4 type disk; allocate auxiliary channel stby type disk; duplicate target database for standby from active database dorecover spfile parameter_value_convert '${V_PRY_SID}','${V_SBY_SID}' set control_files='/opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/ctl/control01.ctl','/opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/redo/control02.ctl' set db_file_name_convert='/opt/oracle/db/db${V_DB_NAME}/${V_PRY_SID}/','/opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/' set log_file_name_convert='/opt/oracle/db/db${V_DB_NAME}/${V_PRY_SID}/','/opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/' set 'db_unique_name'='${V_SBY_SID}' set log_archive_config='DG_CONFIG=(${V_PRIMARY},${V_STANDBY})' set fal_client='${V_STANDBY}' set fal_server='${V_PRIMARY}' set log_archive_dest_1='LOCATION=/opt/oracle/db/db${V_DB_NAME}/${V_SBY_SID}/arch DB_UNIQUE_NAME=${V_SBY_SID} MANDATORY VALID_FOR=(ALL_LOGFILES,ALL_ROLES)' set log_archive_dest_2='SERVICE="${V_PRIMARY}"','SYNC AFFIRM DB_UNIQUE_NAME=${V_PRY_SID} DELAY=0 MAX_FAILURE=0 REOPEN=300 REGISTER VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE)' nofilenamecheck ; } ! V_DATE=`/bin/date` if [ $? -ne 0 ] then         echo ""         echo "${V_DATE} - Error creating STANDBY instance"         echo ""         echo "********************************************************************************" else         echo ""         echo "${V_DATE} - STANDBY instance created SUCCESSFULLY "         echo ""         echo "********************************************************************************" fi sqlplus -s /nolog 1>>/dev/null 2>&1 <<-!         whenever sqlerror exit 1         connect sys/${V_DB_PWD}@${V_STANDBY} as sysdba         alter system set local_listener='(ADDRESS=(PROTOCOL=TCP)(HOST=${SBY_HOST})(PORT=1544))' scope=both;         alter system set service_names='${V_DB_NAME}.eu.roca.net,${V_SBY_SID}.eu.roca.net,${V_SBY_SID}_DGMGRL.eu.roca.net' scope=both;         alter database recover managed standby database using current logfile disconnect from session;         alter system set dg_broker_start=true scope=both; ! ## ## TNSNAMES change, back to Production Mode ## V_DATE=`/bin/date` echo " " | tee -a ${V_LOGFILE}   2>&1 echo "${V_DATE} - Restoring TNSNAMES in PRIMARY "  | tee -a ${V_LOGFILE}   2>&1 echo ""  | tee -a ${V_LOGFILE}   2>&1 echo "********************************************************************************"  | tee -a ${V_LOGFILE}   2>&1 ssh ${PRY_HOST} 'cp /opt/oracle/db/db'${V_DB_NAME}'/soft/db11.2.0.2/network/admin/tnsnames.ora.prod  /opt/oracle/db/db'${V_DB_NAME}'/soft/db11.2.0.2/network/admin/tnsnames.ora' echo ""  | tee -a ${V_LOGFILE}   2>&1 echo "${V_DATE} -  Waiting for media recovery before check the DATA GUARD Broker"  | tee -a ${V_LOGFILE}   2>&1 echo ""  | tee -a ${V_LOGFILE}   2>&1 echo "********************************************************************************"  | tee -a ${V_LOGFILE}   2>&1 sleep 200 dgmgrl <<-! | grep SUCCESS 1>/dev/null 2>&1     connect ${V_DB_USR}/${V_DB_PWD}@${V_STANDBY}     show configuration verbose; ! if [ $? -ne 0 ] ; then         echo "       ERROR: El status del Broker no es SUCCESS" | tee -a ${V_LOGFILE}   2>&1 ;         V_RET=1 else          echo "      DATA GUARD OK " | tee -a ${V_LOGFILE}   2>&1 ; Normal 0 21 false false false ES X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}         V_RET=0 fi Hope it helps.

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  • Update database settings in properties file in Spring

    - by mvg
    Hi all, I am trying to create a Database Manager page which shows the database details on page load and updates the database settings when the user press submit I followed this tutorial and set the database settings in properties file. I managed to update the database settings in properties file programmatically. When I retrieved the database settings using the following code DriverManagerDataSource databaseSource = (DriverManagerDataSource)context.getBean("dataSource"); databaseSource.getUsername(); I managed to get the old value and unable to get the new value This is the mapping in applicationContext.xml file <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location"> <value>classpath:/bundle/database.properties</value> </property> </bean> <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName" value="${jdbc.driverClassName}" /> <property name="url" value="${jdbc.url}" /> <property name="username" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> </bean> I checked the properties file and found it to be updated with the latest input. What am I missing? Thanks in advance P.S I am using JSF1.2 with Spring 3 Update Just making my requirement simple. I am creating a setparate dbsettings page, so that when user wishes to connect to different database he/she can just enter the details in dbsettings page and connect

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  • Taking wrong database configuration array

    - by user309076
    Hi, I have one application in which i have used 2 database connections. In my database config file i have given two arrays as below. $active_group = ‘default’; $active_record = TRUE; FIRST ARRAY $db[‘default’][‘hostname’] = ‘hostname’; .............. .......... SECOND ARRAY $db[‘another_db’][‘hostname’] = ‘hostname’; .............. .......... this is working fine. Now, I copied the entire CI folder to develop another application in which only one database connection needed. So, now, in the database config file, i deleted the second configuration array. But, the db class is taking first application’s second array i.e. “another_db” and it is giving the below error. “You have specified an invalid database connection group.” When i change the default (only one) array name to “another_db” in configuration file. It is working fine. Can’t understand from where it is taking the group name as “another_db”. My application autoloads database library. I have debugged the ci_auto_loader in Loader.php class where it calls $this-database() function with no parameters. But in function database($params, $, $) {}, if I echo $params it shows “another_db”.

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  • Creating multiple instances of a generic database

    - by sagekilla
    Hi all, currently I'm trying to have a setup where a generic database is distributed to students. They would develop an application using this database (Say a shopping cart application), submit their project onto our server, and then it would be graded automatically. These databases are being run in Microsoft SQL Server 2005. We're using user instances to instantiate each database, and multiple requests could be serviced at once. But, the problem is when more than one student submitted a project to be graded, the first database to be instantiated would be the only one and would overwrite all other copies that were currently open. So if stu1 modified his database and stu2 and stu3 had their projects being graded concurrently, at the end of the grading stu1, stu2, and stu3 would have identical DB's at the end. Is there any way I can have multiple independent copies of a generic database, each of which I can load concurrently and modify without having any changes made to any one affecting the others? I did a little reading, and thought it might be possible to do something along the lines of: Student submits project Attach the database with unique db name (specified by student) Do all necessary operations Detach the database I'm unsure if this would fix our problem or be possible, so any help would be much appreciated!

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 5

    - by MarkPearl
    Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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  • Where to store front-end data for "object calculator"

    - by Justin Grahn
    I recently have completed a language library that acts as a giant filter for food items, and flows a bit like this :Products -> Recipes -> MenuItems -> Meals and finally, upon submission, creates an Order. I have also completed a database structure that stores all the pertinent information to each class, and seems to fit my needs. The issue I'm having is linking the two. I imagined all of the information being local to each instance of the product, where there exists one backend user who edits and manipulates data, and multiple front end users who select their Meal(s) to create an Order. Ideally, all of the front end users would have all of this information stored locally within the library, and would update the library on startup from a database. How should I go about storing the data so that I can load it into the library every time the user opens the application? Do I package a database onboard and just load and populate every time? The only method I can currently conceive of doing this, even if I only have 500 possible Product objects, would require me to foreach the list for every Product that I need to match to a Recipe and so on and so forth every time I relaunch the program, which seems like a lot of wasteful loading. Here is a general flow of my architecture: Products: public class Product : IPortionable { public Product(string n, uint pNumber = 0) { name = n; productNumber = pNumber; } public string name { get; set; } public uint productNumber { get; set; } } Recipes: public Recipe(string n, decimal yieldAmt, Volume.Unit unit) { name = n; yield = new Volume(yieldAmt, unit); yield.ConvertUnit(); } /// <summary> /// Creates a new ingredient object /// </summary> /// <param name="n">Name</param> /// <param name="yieldAmt">Recipe Yield</param> /// <param name="unit">Unit of Yield</param> public Recipe(string n, decimal yieldAmt, Weight.Unit unit) { name = n; yield = new Weight(yieldAmt, unit); } public Recipe(Recipe r) { name = r.name; yield = r.yield; ingredients = r.ingredients; } public string name { get; set; } public IMeasure yield; public Dictionary<IPortionable, IMeasure> ingredients = new Dictionary<IPortionable,IMeasure>(); MenuItems: public abstract class MenuItem : IScalable { public static string title = null; public string name { get; set; } public decimal maxPortionSize { get; set; } public decimal minPortionSize { get; set; } public Dictionary<IPortionable, IMeasure> ingredients = new Dictionary<IPortionable, IMeasure>(); and Meal: public class Meal { public Meal(int guests) { guestCount = guests; } public int guestCount { get; private set; } //TODO: Make a new MainCourse class that holds pasta and Entree public Dictionary<string, int> counts = new Dictionary<string, int>(){ {MainCourse.title, 0}, {Side.title , 0}, {Appetizer.title, 0} }; public List<MenuItem> items = new List<MenuItem>(); The Database just stores and links each of these basic names and amounts together usings ID's (RecipeID, ProductID and MenuItemID)

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  • Can a database table be without a primary key?

    - by bodacydo
    Can anyone help me understand if a table in a relational database (such as MySQL) can be without a primary key? For example, I could have table day_temperature, where I register temperature and time. I don't see the reason to have a primary key for such a table. Thoughts? Thanks, Boda Cydo.

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  • Importing wikipedia database dumb - kills navicat - anyone got any ideas?

    - by Ali
    Ok guys I've downloaded the wikipedia xml dump and its a whopping 12 GB of data :\ for one table and I wanted to import it into mysql databse on my localhost - however its a humongous file 12GB and obviously navicats taking its sweet time in importing it or its more likely its hanged :(. Is there a way to include this dump or atleast partially at most you know bit by bit. Let me correct that its 21 GB of data - not that it helps :\ - does any one have any idea of importing humongous files like this into MySQL database.

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  • What's the best way to store a MySQL database in source control?

    - by Marplesoft
    I am working on an application with a few other people and we'd like to store our MySQL database in source control. My thoughts are two have two files: one would be the create script for the tables, etc, and the other would be the inserts for our sample data. Is this a good approach? Also, what's the best way to export this information? Also, any suggestions for workflow in terms of ways to speed up the process of making changes, exporting, updating, etc.

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  • What happened to the "Run" and "Run On" commands in Visual Studio 2010 Database Projects?

    - by Steve Elmer
    Hello, I have migrated a database project from VS2008 to VS2010. While in VS08, I used to be able to right-click on a .sql or .cmd file and select a "Run" or "Run On" command from the context menu. In VS2010, though, these menu items seem to have gone away. I have a number of .sql and .cmd scripts that I am used to being able to run directly from the Visual Studio IDE. Can someone point me in the right direction? Thanks, Steve

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